Grinding disk

ABSTRACT

The invention relates to a grinding disk with zones of increased strength. These zones are aligned in the radial direction of the disk and adjoin the hub of the disk and stretch at the most up to two-thirds of the radius of the disk. The type of bond of the zones of increased strength is the same as that of the proper and suitable grinding layer. The zone of increased strength and the normal grinding layer have different fillers.

United States Patent [191 Bogusch GRINDING DISK [75] Inventor: Erich Bogusch, Schwaz, Austria [73] Assignee: Tyrolit-Schleifmittelwerke Swarovski K.G., Schwaz, Austria [22] Filed: Aug. 28, 1973 [21] Appl. No.: 392,328

[52] US. Cl. 51/206 NF [51] Int. Cl. B24D 5/04; B24D 5/14 [58] Field of Search 51/204, 206 R, 206 NF, 51/209 R, 209 DL [56] References Cited UNITED STATES PATENTS 687,962 12/1901 Hyde 51/206 R 1,336,751 4/1920 Linbarger 51/206 R 2,004,630 6/1935 Krug 51/206 R 2,006,308 6/1935 Bush 51/206 R 51 Aug. 12, 1975 2,092,591 9/1937 Sohlstrom 51/206 NF 2,097,803 11/1937 Sanford 51/206 R 2,102,343 12/1937 Whitcomb 51/206 R 2,624,660 l/l953 Teague 51/206 R X 3,263,377 8/1966 Charvat 1 51/206 NF X 3,526,063 9/1970 Cook 51/206 NF Primary ExaminerDonald G. Kelly Attorney, Agent, or Firm-Wenderoth, Lind & Ponack 5 7] ABSTRACT The invention relates to a grinding disk with zones of increased strength. These zones are aligned in the radial direction of the disk and adjoin the hub of the disk and stretch at the most up to two-thirds of the radius of the disk. The type of bond of the zones of increased strength is the same as that of the proper and suitable grinding layer. The zone of increased strength and the normal grinding layer have different fillers.

4 Claims, 9 Drawing Figures PATENTEnAumms 3, 898,773

sum 5 Fig. 9

GRINDING DISK BACKGROUND OF THE INVENTION The invention relates to a grinding disk for highspeed grinding with a zone of increased strength within the part of the grinding article which adjoins the borehole of the grinding disk, of up to two-thirds of the ra dius of the disk. The zones of different material strength overlap one another in the radial direction within the radial length of the zone of increased strength, with at least one zone having the strength and composition of the grinding layer.

The present stage of research and practice proves that an increase in the speed of rotation of a grinding disk involves an essential improvement with regard to the metal removal rate and/or the surface quality of the workpiece and with regard to reduced wear of the grinding disk and the necessary cutting power.

Moreover, improvements in the quality of the workpiece can be noticed, which partially make the preliminary treatment and the aftertreatment involved in traditional procedures unnecessary.

An essential advantage of high-speed grinding is that the duration of the grinding operation is considerably reduced because of the better metal removal rate which effects improved economy.

Due to kinetic energy appearing in a rotary grinding disk, high-speed grinding involves safety problems, especially with regard to the grinding disks to be used.

As is well known, the kinetic energy increases quadratically with the diameter of the disk on the one hand and with the rotational speed of the disk on the other hand. An increase in the speed of grinding disks from 30 to 60 m/sec causes a fourfold increase of the kinetic energy.

Therefore it is only natural that the highest and special quality standards are required of grinding disks which will be subjected to high-speed grinding operations.

In order to be acceptable, grinding disks for highspeed grinding operations, that is to say for operations with the peripheral working speed of the disk being, for example, 60m/sec and 80m/sec, must be resistant to centrifugal forces acting at a peripheral speed of 120m/sec and 150m/sec. As is already known such peripheral speeds cannot be achieved, according to the present state of technology, with grinding articles which have been consolidated in the ordinary way and which have a vitrified bond.

As can be mathematically proved, the strongest tangential or bending strain caused by the centrifugal forces acts on the periphery of the borehole f the grinding disk. This knowledge has led to the production of disks without boreholes. Up to now, however, such disks have not been satisfactory in the field of precision grinding.

Other experiments to absorb the tangential strain appearing at the periphery of the borehole rely on a zone of increased breaking strength on the periphery of the borehole. This zone of increased breaking strength may be achieved by changes in the composition, by soaking of the peripheral zone, for example, with synthetic resin, as well as by glueing in rings, for example, metal rings.

Because of too weak glueing points, because of cracks in the glueing spots, and with disks with a zone of increased breaking strength of ceramic material because of shrinkage cracks, the rejection rate in production of such disk has heretofore been extremely high.

The same disadvantage also occured with metal or plastic hubs with lateral radially stretching cover leaves.

SUMMARY OF THE INVENTION It is therefore the object of the invention to create a grinding disk without such disadvantages.

According to the present invention this is achieved in that at least one zone of increased strength has the same type of bond as the primary grinding layer, but has a different filler.

The zone or the zones of increased strength are preferably planned in the peripheral direction.

The zones of increased strength are preferably constant in width.

In an embodiment of the present invention the zone or the zones of increased strength are of ceramically bound fine grain. It is advantageous if the zone or the zones of increased strength have a different coefficient of expansion compared with the primary grinding layer of the grinding article or disk.

It is also planned to provide the zone of increased strength with prestressing.

The invention will now be described in detail with regard to the figures of the accompanying drawings, without however the invention being limited thereto, as several changes and modifications are possible within the scope and nature of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 to 8 show cross sections through various embodiments of a grinding disk according to the invention, and FIG. 9 shows a cross section along line I-I of FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION The grinding disk 1 consists of a primary zone of normal and proper grinding material 2 and one or several zones of increased strength 3.

The zones of increased strength 3 are solely an alteration of the proper grinding material compound in this zone. It has to be noticed that these zones, although they correspond to supporting elements, are by no means limited to this function. That is to say, under certain circumstances zones 3 may come into contact with the workpiece and even take active part in the cutting or grinding process.

As can be seen from FIGS. 1 to 8 the zones of increased strength 3 may for example form separate radially extending disk-shaped elements or strips (FIGS. 1 and 5), but there may be a single zone of increased strength as well, placed centrally in disk 1 and surrounded on both sides by the grinding compound of the primary grinding zone 2 of the grinding disk 1 (FIG. 3). The zones of increased strength 3, however, may also be formed as a hub-like coating 4 within the range of the borehole 6, with the individual zones of increased strength stretching radially into the grinding article 1, thus forming a coherent set of disk-shaped elements.

Of course the zones of increased strength 3 may also have cutouts 5 along their peripheries, as can be seen from FIG. 9.

It is an essential part of the invention that the zones of increased strength and the zone or the zones of the strength and composition of the grinding layer of the grinding disk 1 overlap to a certain extent, B or B, along the radial length of the zone of increased strength.

Preferably, the increased strength material is a material of a fine grain with a vitrified bond, the fine grain being of finer granulation than the material of the grinding layer.

Also, the increased strength material may have armoring webs.

Further, zone of increased strength material may be axially and radially prestressed.

What I claim is:

1. In a grinding disk for high-speed grinding and having an axial borehole therethrough and having a primary grinding layer formed of a grinding material of a desired grinding strength, the improvement comprismg:

a ring-shaped zone of increased strength material adjoining said borehole of the grinding disk, said zone of increased strength material comprising at least one disk-shaped element extending radially from said borehole no more than two-thirds of the radius of said disk, each said at least one disk-shaped element having a pair of parallel surfaces formed by planes extending radially outwardly from said borehole and a cylindrical surface joining said pair of parallel surfaces, the axial thickness of said diskshaped element being less than the axial thickness of said disk, said grinding material and said material of increased strength overlapping one another in the radial direction of said disk within said zone by a radial distance equal to at least a major portion of the radial length of said zone, contact between said grinding material and said at least one disk-shaped element in said zone being only at said cylindrical surface and at least one of said parallel surfaces, and said increased strength material having the same type of bond as the said grinding material of said grinding layer but a different filler therefrom.

2. In a grinding disk as claimed in claim 1, wherein said at least one disk-shaped element comprises at least two such elements of increased strength material separated from each other in the axial direction of said disk.

3. In a grinding disk as claimed in claim 1, wherein said zone comprises a hub shaped coating surrounding said borehole and said at least one disk-shaped element extending radially outwardly therefrom.

4. In a grinding disk as claimed in claim 1, wherein said zone of increased strength material comprises material of a fine grain with a vitrified bond, the fine grain being of a finer granulation than the material of said grinding layer. 

1. In a grinding disk for high-speed grinding and having an axial borehole therethrough and having a primary grinding layer formed of a grinding material of a desired grinding strength, the improvement comprising: a ring-shaped zone of increased strength material adjoining said borehole of the grinding disk, said zone of increased strength material comprising at least one disk-shaped element extending radially from said borehole no more than two-thirds of the radius of said disk, each said at least one disk-shaped element having a pair of parallel surfaces formed by planes extending radially outwardly from said borehole and a cylindrical surface joining said pair of parallel surfaces, the axial thickness of said disk-shaped element being less than the axial thickness of said disk, said grinding material and said material of increased strength overlapping one another in the radial direction of said disk within said zone by a radial distance equal to at least a major portion of the radial length of said zone, contact between said grinding material and said at least one disk-shaped element in said zone being only at said cylindrical surface and at least one of said parallel surfaces, and said increased strength material having the same type of bond as the said grinding material of said grinding layer but a different filler therefrom.
 2. In a grinding disk as claimed in claim 1, wherein said at least one disk-shaped element comprises at least two such elements of increased strength material separated from each other in the axial direction of said disk.
 3. In a grinding disk as claimed in claim 1, wherein said zone comprises a hub shaped coating surrounding said borehole and said at least one disk-shaped element extending radially outwardly therefrom.
 4. In a grinding disk as claimed in claim 1, wherein said zone of increased strength material comprises material of a fine grain with a vitrified bond, the fine grain being of a finer granulation than the material of said grinding layer. 